Mechanisms of Charge Trapping at a Dielectric Surface: Resonance Stabilization and Dissociative Attachment

A solid Kr film partially covered with O₂ molecules is charged by a 0- to 10-eV electron beam. The electron energy dependence of the trapping cross section indicates that surface charging in the 0-2-eV range is due to stabilization via the ²ΠgO₂^- resonance, whereas in the 4-10-eV region, it is due to O^-(²P) formed by dissociation of the intermediate ²Πᵤ state of O₂^-.